Method for machining with a lathe and more particularly for copying and a tool-carrier making it possible to implement such a method

Abstract

Method for machining with a lathe and more particularly for copying and a tool-carrier making it possible to implement such a method. The tool-carrier may be installed on the trolley of a lathe comprising a tool support sliding between two guides and rotating about an axis orthogonal to the guides. Periodically the support is moved away from a stop fixed to the guides and returned back against the stop. The point of the tool thus describes, in both directions, a small arc of a circle centered on the axle.

I claim: 
     
       1. In a method for machining with a lathe and more particularly for copying, including the steps of driving the workpiece to be machined in rotation about an axis and driving the point of the tool, in relation to the axis, in two movements in a working plane passing through the said axis, the first movement being in two directions one of which is parallel to the said axis, and the second movement being a relative cyclic movement having a period of T and a slight amplitude in relation to the dimensions of the work-piece, the improvement wherein said cyclic movement comprises the following three phases: a first phase I during which the point of the tool moves away from the work-piece starting from a point of origin O and reaching a maximum travel point M following a plane curve C whose tangent at the point of origin O is substantially parallel to the said axis,   a second phase I' during which the point of the tool comes back from the point of maximum travel towards the point of origin O following the curve C, and   a third phase J during which the point of the tool remains at the point of origin O.   
     
     
       2. The method for machining with a lathe according to claim 1, wherein the curve C is a portion of a quarter circle. 
     
     
       3. The method for machining with a lathe according to claim 1 wherein the duration j of the phase J is at least equal to twice the duration i during which the phases I and I' take place. 
     
     
       4. A tool carrier which may be installed on the trolley of a lathe, comprising: two parallel guides (11, 12) fixed relative to the body (13) of the tool-carrier (10),   a mobile tool support (14) installed between the two guides (11, 12) for rotation about an axis (15) orthogonal to the guides (11, 12) and fastened at its ends to these guides,   a stop (20) fixed to the body (13) of the tool-carrier (10),   a return means (21) for driving the tool support (14) back against the said stop (20), and   means (22) for periodically moving the said support (14) away from the said stop (20).   
     
     
       5. The tool-carrier according to claim 4, wherein: the means (22) for moving the support away comprises: a drive shaft (24);   an excentric (25) driven in a rotating movement about an axis parallel to the guides (11, 12) by the drive shaft (24) with the periphery of the said excentric (25) coming periodically into contact with the support (14) for moving the latter away from the stop (20).   
     
     
       6. The tool-carrier according to claim 4, wherein: the means (22) for moving away comprises: a drive shaft (24');   an excentric (25') driven in a rotating movement about an axis parallel to the guides (11, 12) by the drive shaft (24');   a crown wheel (31) surrounding the excentric (25') and rotatable about the excentric and having, on its external periphery, at least one protrusion (38) for contacting said support (14); and   means (35) for coupling the drive shaft (24') to the said crown wheel, (31) to make the crown wheel (31) rotate in the reverse direction to the excentric (25').   
     
     
       7. The tool-carrier according to claim 6, wherein the coupling means (35) includes means for reducing the rotation speed between the crown wheel (31) and the drive shaft (24'). 
     
     
       8. The tool-carrier according to claim 7, wherein: the coupling means (35) comprises a small mobile toothed wheel (37) mounted for rotation about the excentric (25') on crown wheel (31) and driven by the drive shaft (24'), and a large toothed wheel (36) fixed to the body (13) of the tool carrier, with the small toothed wheel (37) rotating on the inside periphery of the large toothed wheel. 
     
     
       9. The tool carrier according to claim 6 wherein in the crown wheel (31) comprises several protrusions (38, 38'; 38") spaced out irregularly along its periphery. 
     
     
       10. The tool carrier according to claim 5 wherein the drive shaft (24, 24') is driven in a rotating movement by a motor (23, 23') installed in the body (13) of the tool-carrier.